the Perphiral Auditory System (PAS)

Question 1

parts of PAS

Answer 1

1. External Ear
2. Middle Ear
3. Inner Ear

Question 2

Functions of External Ear (5)

Answer 2

1. Collect Sound
2. Amplify Sound
3. Transfer Sound
4. Protect Middle & Inner Ear
5. Sound Localisation

Question 3

Parts of External Ear (2)

Answer 3

1. Auricle

2. External Acoustic Meatus

Question 4

Auricle

Answer 4

the external ear shape & structure

made from skin & cartilage

aids w. sound localisation

Question 5

External Acoustic Meatus

Answer 5

tube between aricle and tympatic membrane

lateral 1/2=cartilage, medial (inner) 1/2=bone

approx 0.7cm diameter, 2.3cm length

amplifies sound

Question 6

what does the cartliage area of external acoustic meatus contain?

Answer 6

hairs and glands secreting CERUMEM (ear wax)

collects debris protecting internal structures

Question 7

Structures of the Middle Ear (3)

Answer 7

Tympanic Membrane

Ossicles

Eustachian Tube

Question 8

Functions of Middle Ear (3)

Answer 8

1. Protect Inner Ear
2. Equalise air pressure- ensuring max sound vibrations are transferred
3. Act as a Impedance Acting Device by transfering energy to inner ear

Question 9

Middle Ear as an Impedance Acting Device

Answer 9

amplifies sound waves to ensure optimum energy transfer via:

change in SA b/t tympanic membrane (large SA) and foot palate (small SA)

Lever action using length of incus & staples

Question 10

Tympanic Membrane

Answer 10

(ear drum)

thin membrane seperating external & middle ear

sound waves cause it to vibrate

differeniates sound frequency + pitch via speed of vibration

Question 11

what are the ossicles?

Answer 11

3 small moveable bones:

1. Malleus
2. Incus
3. Staple

Question 12

what is the function of the ossicles?

Answer 12

convert sound wave vibrations from tympanic membrane to mechanical vibrations

Question 13

what is the Eustatian Tube (ET)?

Answer 13

a thin tube connecting the middle ear and nasopharynx

Question 14

function of Eustatian Tube?

Answer 14

equalise air pressure either side of the tympanic membrane allowing max. energy transference

Question 15

what does the Eustatian tube do during chewing & swallowing?

Answer 15

it opens

Question 16

Parts of the Inner Ear (2)

Answer 16

1. Cochlea

2. Vestibular System

Question 17

Structure of the Cochlea

Answer 17

Auditory nerve joins

spiral ganglion

2-3 turns of fluid filled tubes which are sperated via membranes:

1. Upper Scala Vesticula: containing perilymph fluid
2. Middle Scala Media: containing endolymph fluid and organ of corti
3. Lower Scala Media: containing perilymph fluid

Question 18

significanace of fluid type in the cochlea

Answer 18

the Upper scala Vesticula + Lower scala media contain perilymph fluid, but the Middle Scala Media contains endoplymph fluid

Perilymph and Endolymph have DIFFERENT ELECTRICAL POTENTIALS which send different signals to the brain

Question 19

What does the Organ of Corti contain? (3)

Answer 19

contains inner + outer hair cells which are receptive to sound via contraction

contains supporting cells

Question 20

what happens to the hair cells in the organ of corti if exposed to very loud noise?

Answer 20

they can be damaged resulting in hearing loss

Question 21

functions of the organ of corti (2)

Answer 21

1. Transform sound vibrations into electrical signals

2. Active Cochlea Mechanism